Well the large black lettering “Straßenbahn Haltestelle” means, well, “tram stop.” Good to know.
On top of the main oval sign, there’s a smaller sign – in this case saying “Ottakring.” That’s the name of the stop or station.
The number 46 and the letter J are the names of the two tramlines that halt at this stop.
The letter N with the cat’s eyes indicates that a special night tram service stops here, too.
Below those symbols you’ll see a timetable for the relevant trams, giving the names of the stops on the line, the time it takes to reach stops further along the line and the intervals between trams for various periods of the day.
That metal thing’s a garbage bin.
What you can’t see in that photo, but you can in the one at the top are two smaller signs pointing out from the post. These repeat the number or letter of the tram’s line, point in the direction the tram leaves from the stop, and list the name of the last station on the line.
In this case, the 43 tram goes to Schottentor. The U symbol tells you there is a subway (U-Bahn) at Schottentor. (The N43 is the nighttime version of the 43.)
Incidentally, the bus stops follow exactly the same structure and use the same markings. The only difference is that it says “Autobus Haltestelle” instead of “Straßenbahn Haltestelle” on the top of the post.